This invention relates to a system for recognizing the ID numbers of cassettes or the like in a semiconductor manufacturing system in a clean room for manufacturing semiconductor wafers, liquid crystal display boards, reticles, disks, etc. (hereinafter referred to as "an ID recognizing system", when applicable).
One example of a semiconductor manufacturing system of this type is as shown in FIG. 8. In FIG. 8, reference numeral 1 designates a surface treatment device incorporating a surface treatment furnace for giving surface treatment to semiconductor wafers, the device 1 having two ports (described later) arranged in parallel; 2, a wafer inspecting device; 3, a self-running type positioning robot; 4, a wafer storehouse; 4A, the apron (or entrance) of the wafer storehouse 4; a wafer washing device; and 6, a linear motor conveyor.
FIG. 9 is a sectional view of the aforementioned surface treatment device 1. In FIG. 9, reference numeral 10 designates a closed container with an opening 11 which is sealingly closed through a seal 12 with a lid 13. The lid incorporates an automatic locking mechanism (not shown) with a rod 14. The rod 14 is moved back and forth, so that its end is engaged with the opening 11 of the container 10. Further in FIG. 9, reference numeral 15 designates a wafer cassette, in which a plurality of semiconductor wafers W (for instance twenty-five semiconductor wafers W) are set one above another. The wafer cassette 15 is set in the container 10 when conveyed. FIG. 9 shows the container 10 including the wafer cassette 15 which container is placed on a plate 16 of the surface treatment device 1. The plate 16 forms the above-described port (or cassette taking-in-and-out ports) 16A. The container 10 is locked onto the plate 16 with lever-type locking mechanisms 17, and thereupon the self-locking mechanism of the lid 13 is released. The wafer cassette 15 together with the lid 13 is placed on the stand 18 of a lift 18 and moved downwardly, and then only the wafer cassette 15 is conveyed to the surface treatment furnace (not shown) by the conveyor. After the surface treatment of the semiconductor wafers has been accomplished, the wafer cassette 15 is moved back to the lift stand 18A on which the lid 13 has been left. Thereafter, the lift stand 18A is moved upwardly, so that the wafer cassette 15 is brought into the container 10. Under this condition, the lid 13 is locked; that is, the container 10 is closed with the lid 13 thus locked. The container 10 thus closed is moved to the apron 4A of the wafer storehouse 4 by the robot 3. In the wafer storehouse 4, a stacking crane 7 is operated to set the container 10 at a predetermined position on a shelf specified by a central control device (not shown).
Semiconductor wafers or the like should be free from dust. Therefore, a semiconductor manufacturing process is carried out in a clean room having a clean atmosphere, and heretofore the wafer cassette 15 is not covered when conveyed from one processing device to another. However, as the integration of semiconductor circuits is improved, the wafer cassette 15 is handled as follows: That is, the wafer cassette 15 is set in the closed container 10 before moved between processing devices. In addition, the closed container 10 is filled with inert gas, to suppress the formation of natural oxide films on the semiconductor wafers.
The wafer cassette 15 is moved from one processing device to another and from one processing station to another. Therefore, it is essential to read the identification (ID) of the wafer cassette 15 to determine what the latter contains. In most of the conventional cassette recognizing systems, an ID number of bar-code type affixed to the wafer cassette is optically read. In another system, a surface elastic wave is utilized to read the ID number, in a non-contact mode, from a tag affixed to the wafer cassette 15.
As was described above, in the conventional system, the ID number is of bar-code type, and it cannot be rewritten without changing the bar code. That is, in order to change it, a new bar code label must be affixed to the wafer cassette. The base plate of the bar code label forms a protrusion on the surface of the cassette or container which obstructs the self cleaning operation, with a result that a chemical washing operation cannot be carried out.
On the other hand, in association with CIM, it has been demanded that data such as the manufacture history and conditions of a wafer cassette be transferred together with the cassette and the container. However, the bar code system, being small in the quantity of data to be handled thereby, cannot satisfy this demand.